I've used a drobo (proprietary raid) attached over my network and have been more than pleased with its ease of use, and flexibility. It can be pricy compared to just a simple external harddrive but I think it's worth its weight in gold so to speak. They have several models available now, check'em out. http://www.drobo.com/products/index.php

Nearly four years on the QNAP TS639 Pro I referred to a few posts earlier in the thread has continued to give trouble-free service. QNAP have also been active over the years, even once the product was superseded, with firmware updates. I initially populated the box with 4 x 1.5TB drives (1TB = a million million bytes) giving a RAID 5 capacity of 4TB. RAID 5 offers fault tolerance - a drive can fail without loss of any data. I never thought I'd need more but, in the best Dickensian tradition, more was called for! I could have added a further two 1.5TB drives but with the originals being regular, rather than enterprise, grade drives and four years old to boot I decided to bite the bullet and buy 4 x 3TB drives plus a spare, this time opting for drives rated for 24/7 usage.

The upgrade required me to hot swap the four drives, one at a time, allowing the RAID 5 array to rebuild between swaps. That took eight hours per drive during which time I was a little nervous as a drive failure during the day and a half or so that the whole procedure took would have meant me digging out my off-line backups and starting from scratch. With the four new drives in place the NAS capacity went from 4TB to, er, 4TB.

Actually, that was expected and the last stage was to instruct the NAS box to use the extra capacity. That was another slightly scary moment as the progress indicator started at 25% and then took about an hour to get to 28% at which point I went to bed. Happily things speeded up overnight and I now have the full 8TB available, all the original bytes being preserved.

I think this is a win for having a dedicated NAS box. My choice was to go for a commercial option rather than a self-build but however you slice it the opportunity to perform a significant capacity upgrade with all the original data intact is very handy. I'm not even sure 3TB drives were available when I bought the NAS and even if they were they would have been totally unaffordable. I could have opted for 4TB drives this time around but cost wise they didn't make sense, especially as I still retain the option to add another couple of 3TB units to the two spare drive bays.

Bottom line: don't be put off by the high initial price of a Network Attached Storage device. Get a good one and you'll get a level of ongoing support that seems rare these days and you can refresh it in a few years time as and when larger hard disks become available at affordable prices.

Update: And rather than throw away those 1.5TB drives I've just ordered a QNAP TS-412 to put them in. It's a bargain basement unit and I can use it as an off-line (normally unpowered as those disk drives are getting on a bit) back up for my data with the disk drives configured as JBOD (Just a Bunch of Disks) for the best part of 6TB of peace of mind. Recycling rocks.

Interesting post Bob, as in another thread I have been debating going NAS myself. While I was looking at the Drobo 5N, in a general search I did come across the QNAP range but didn't know anything about them really. As far as I can tell the software in the QNAP series are less flexible if I wanted to use mismatched drives, but I'm not sure how critical that is anyway. Maybe I should see a NAS as just somewhat fixed once started, and not something to tinker with.

I can't speak to which manufacturer is currently the best but I stuck with QNAP for the TS-412 box to reuse those old disks because I have no reason to change and the price (£260) was right. My only tip would be that if the choice is between a quiet box or one that offers the last ounce of transfer speed then go for silence unless the box is going to be housed away from the main living areas!

One minor correction: In my update to my last post I said JBOD but I really meant RAID 0 as I won't need redundancy and the consequences of the increased chance of a disk failure bringing down the entire virtual disk are acceptable for my intended use.

Temperature shouldn't be an issue. My TS-639 Pro is quiet and with four of the bays occupied the disks are all within a degree of 30 C, about 15° above ambient. Not that they are doing much at the moment but that is probably what most NAS devices spend their time doing, or not doing.

The baby NAS, a QNAP TS412, arrived today enabling me to reuse the four HDDs which were originally in my TS-639-Pro. I had to manually reboot it after the initial firmware upload because I think (but I'm not sure) it recognised the configuration of the drives and was trying to rebuild the original data. Very clever but not what I wanted as these drives needed to be reconfigured as RAID 0 rather than the original RAID 5.

After the reboot setup was a breeze and I quickly created the RAID 0 volume and assigned the necessary permissions allowing full access from Windows Explorer.

A bonus I had hoped for, but it's always best not to count the chickens, is that with both NAS devices connected to the network via a switch I have been able to create some direct NAS to NAS replication jobs. That allows me to backup data on the TS-639 Pro to the TS412 via the network without the need for that data to flow through the main computer: I can set the replication in train and then switch off the computer and just let the NAS devices get on with it. Once done I'll power down the TS412 until a further incremental backup is required, maybe something I'll only do a few times a year unless prudence dictates otherwise.

I suspect that this sort of replication is only possible because both devices are made by the same manufacturer. Anyway, I'm a happy bunny as I've found a use for those old drives (now giving 5.5TB of formatted RAID 0 storage compared to their original 4TB of RAID 5) for little more than the cost of one of the new 3TB drives I fitted to the TS-639-Pro. Result.